The Design And Analysis Of Attribute-based Encryption Algorithms

With the rapid development of cloud computing techniques,the cloud storage service is so popular that is used by more and more people.The cloud storage service can not only reduce the storage costs for the data owners,but also efficiently realize data sharing among different users.However,in a cloud storage system,once the data owners store local data in the cloud,they inevitably lose control over the data,this may cause the reveal of the data.For example,the cloud service provider can peek at the sensitive personal data,and even disclose these data to the users who have no access rights.How to achieve data confidentiality and access control simultaneously is a major challenge for cloud storage service.Attributebased encryption(ABE)is a promising encryption technique for secure and fine-grained access control in a cloud storage environment,and has become a research hotspot in public key cryptography.Depending on different application and security requirements,after investigating the multiauthority,efficiency,key abuse and user revocation issues in ABE,we design several ABE algorithms with distinct functional advantages.The main contributions of this work can be listed as follows:1.One efficiency drawback of ABE is that the number of resource-consuming pairing operations required to decrypt a ciphertext grows with the complexity of the access policy,which presents a significant challenge for the users who decrypt data on mobile devices.Outsourced decryption for ABE has been presented to address this problem.However,available ABE schemes with outsourced decryption have two main limitations: first,all the schemes were constructed in the single-authority setting;second,the schemes were only proved to be selectively secure.Towards this end,after proposing the security model for multi-authority ABE schemes with outsourced decryption,we present a multi-authority ABE scheme with verifiable outsourced decryption,and further prove that it is adaptively secure by a direct black box reduction.Extensive efficiency analysis results indicate that our scheme requires no pairing operations and is suitable for user decryption on mobile devices.2.In a multi-authority ciphertext-policy ABE(CP-ABE)scheme,a user's secret key is associated with his attributes and issued by several authorities who manage different specific sets of attributes;a ciphertext which is associated with an access policy can only be decrypted by the users whose attributes satisfy the access policy.As multiple users may have the same attributes and decryption privileges,a misbehaving user can sell his secret key to others,without worrying to be caught.To address this issue,we present a traceable multi-authority CP-ABE scheme,and further prove that it is statically secure in the random oracle model.Compared with existing traceable multi-authority CP-ABE schemes,the proposed scheme has four advantages: first,the attributes are not fixed at setup and the attribute universe is not bounded to polynomial size;second,the ciphertext polices can be expressed as any monotone access structures;third,the proposed scheme is constructed in prime order groups,which makes this scheme more efficient than those in composite order bilinear groups;finally,the proposed scheme requires neither a central authority nor an identity table for tracing.3.Efficient user revocation remains a challenging problem in multi-authority attributebased encryption.To solve this problem,we present a multi-authority CP-ABE scheme with efficient revocation,and further prove that it is statically secure and revocable.Compared with existing revocable multi-authority CP-ABE schemes,the proposed scheme significantly reduces the computation and storage costs for the users.In addition,the proposed scheme supports large universe and any monotone access structures,which makes it more flexible for practical applications.4.To address the problems that the traditional ABE schemes cannot support user accountability and have huge computational burden for data owners,we construct an online/offline traceable CP-ABE scheme in prime order bilinear groups,and further prove that it is selectively secure in the standard model.If a malicious user leaks his secret key to others for benefit,he will be caught by a tracing algorithm in our proposed scheme.Extensive efficiency analysis results indicate that the proposed scheme moves the majority cost of an encryption into the offline encryption phase and is suitable for user encryption on mobile devices.5.In a CP-ABE system,the access policies will reveal some sensitive information of the receivers and the issue of key abuse could pose a risk to the safety of users data.A few CP-ABE schemes which achieve traceability and hidden policies simultaneously have been presented to address these problems.However,state-of-the-art CP-ABE schemes with traceability and hidden policies have two main limitations: first,all the schemes only support policies expressed in “AND gate”;second,the schemes were only proved to be selectively secure.Towards this end,this paper presents a traceable and hidden CP-ABE scheme where the access polices can be expressed as any monotone access structures,and further proves that the proposed scheme is adaptively secure.